/Engine/Source/Runtime/RHI/Public/RHICommandList.h
Dispatches work to the RHI thread and the GPU. Also optionally waits for its completion on the RHI thread. Does not wait for the GPU.
void ImmediateFlush ( [EImmediateFlushType::Type](API\Runtime\RHI\EImmediateFlushType__Type) FlushType )